text:
Do I need a license to flight test a homebuilt seaplane at very low altitude?
I am asking this because me and my friends are building a homemade seaplane or boat whatever you want to call it. It's not designed for long-range or high-altitude flights. We're not going to fly at a typical altitude of normal planes/seaplanes but we're just flying it to test it. Do we require a license to fly it?
This is in Canada and it's a manned aircraft.

How big/ heavy is it?

take a look at ultra-light category, if your build matched the description you might be able to fly it without a license.

Welcome to aviation.SE! I edited your question to - hopefully! - make it a little clearer. If I got it wrong, feel free to edit again or roll back. The [tour] may be helpful if you're new to StackExchange.

14 CFR §1.1 defines an aircraft as “means a device that is used or intended to be used for flight in the air.”  Flying boats are intended for flight in the air.  Therefore.....

I'm not sure that this answers the question. There are a number of things defined as an aircraft by 14 CFR 1.1 (for example a Drone, an Ultralight, hang glider, powered parachute, or even a kite) that do not require a license to fly.

Also, the OP says it's not going to fly "at an average height of normal planes/seaplanes" (whatever that means), so maybe it's a hovercraft or ekranoplan?

The OP added the information that this is about Canadian regulations.

I'm puzzled how an answer citing a US regulation can be helpful to someone in Canada. It's certainly possible that Canada has a very similar definition, but this answer on its own is about the US.


text:
Is there a common route that Seattle GA pilots use to circle Mt Rainier while avoiding class B airspace?
I'd like to fly around Mount Rainier in a C172 out of Renton (KRNT). What route do people usually take? I wonder if I can climb quickly enough once out of Seattle class B airspace for terrain around Mt Rainier. What do people usually do?

At what altitude are you wanting to fly around it? Do you have mountain flying experience?

Only a little bit of mountain flying training in New Zealand..  at 10,000

If you don't get a good answer here you might try a discussion board or the FATPNW Facebook group. I suspect there may be different opinions on this.

I fly out of BFI and RNT.  The short answer is go East to clear the B, then South to parallel terrain as you climb.  You will have more time to do this if there is a North flow.
There’s no specific route per se, just climb as best you can while keeping between the two.
The Lake Youngs departure gets you going in the right direction, and once just past Enumclaw you can make a circling climb to get comfortably above the ridges.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
Can I use a rental airplane to conduct air tours?
Can a commercial pilot perform non-stop air tour operations under part 91 within 25SM of the airport using a rental airplane from the FBO?
I noticed that in the LOA application, the operation needs to provide:

Type of aircraft, registration number(s), and make/model/series;

I wonder if this has to be the operator's own aircraft?

Welcome to aviation.SE!

Beyond the aviation angle of this question there are legal liability and insurance concerns common to any business that ought to be addressed.  Any person renting equipment ostensibly for personal use, but in reality is using it to run a business on the side, ought to have a commercial lease agreement in place with the owner of the equipment.  Have you spoken with the FBO about your plans?
Regarding aviation specifics, these sort of questions have come up before and the CFRs don't offer much in the way of ownership requirements for aircraft involved in commercial operations.  Own vs lease just doesn't seem too critical from an operational standpoint as far as the Feds are concerned.  I won't start another "holding out" discussion here, but you should definitely talk to the FBO about your plans before moving forward with this idea.

Your points about insurance etc. are spot on. Non-stop air tours within 25SM can be done under part 91, however. They're one of the exceptions in 119.1(e) that don't require an air carrier certificate. They're still a commercial operation, though.

Thanks for pointing that out Pondlife, I guess I could benefit from my own advice regarding getting into the FARs!  I will edit...

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Can I request a visual approach before I have the field in sight?
I was on an IFR flight plan in VMC. The ATC asked me what approach I wanted, and I said visual approach. He said expect RNAV approach instead without saying why. I wonder if it's okay to ask for vectors for visual approach when you are still far out and have no visual yet, or it's expected to ask for an IAP first and then ask for visual when you have the field in sight? Thanks!

Please limit your usage of acronyms (or expand/explain them), as not all readers are pilots. Some are simply enthusiasts or looking to expand their personal knowledge.

More context would be helpful. Was this at JFK or ALO? At three pm or midnight? When you say "VMC" was it marginal or clear-and-a-million?

Which country are you asking about? The regulations or procedures may be different in different places.

It's a busy class D airport under a class B shelf in the US. It was in day time with clear sky and 10sm visibility.

The answer to this question really has to do with shared expectations between pilots and controllers with regards to workload.  Let’s consider two scenarios:
Before the field is in sight – (your question)  As an instrument rated pilot, on a filed flight plan with an appropriate equipment code, ATC expects you to be capable of following a published approach procedure to navigate yourself to a position from which you can make a landing.  If you are asking a visual approach before you are in a position to accept it, (i.e. need vectors) you are in essence telling the controller that you are either unable, or just don’t feel like doing so.  Instead, you want them to do the work for you to get set up on final.
Workload permitting they may be happy to oblige, or they may vector you anyway for separation, but they are not required to navigate for you.  However, if you have an equipment malfunction you are required to let them know, and declare “unable” for any approach they might try to clear you for that you cannot comply with.
Field/Traffic in sight – In this case the controller might look favorably upon your request because visual approaches put some responsibility for maintaining separation on the pilots.  (if you report the traffic you are following in sight you are required to maintain adequate separation from it, not ATC.)  This may help them out some, and they would really have no reason to deny you the approach request.  But if for any reason they did deny the visual, you would have two options:

Just continue to fly the published approach you were cleared for.  Once you are VMC with the field in sight you will have met the criteria for descending below published mins, so there is really nothing stopping you from proceeding by using primarily visual reference at any time after that.  Just make sure you continue to monitor the instruments for guidance.  And to the best of your ability it would be wise to continue to comply with all procedure altitudes, VDP, etc.  (FYI, most airlines require pilots flying a visual approach to have an instrument procedure loaded and to use it for guidance.)
Cancel IFR.  Switching to a visual approach while still on your IFR clearance really serves no purpose once you have the field in sight.  And if you fly IFR into untowered airfields on a regular basis, it might be a good habit to get into canceling IFR airborne as soon as you have the field in sight to prevent forgetting to call and cancel your flight plan after landing.

In short, by requesting a visual approach before you have the field in sight you are making more work for ATC, (making them less apt to clear you...) but requesting or accepting a visual after the field is in sight you may be helping them.
ADDENDUM:
I had an afterthought...  If you don't want to be bothered loading, activating, flying a (possibly complex) approach that you have no need for and don't really want, yet you want to remain on your IFR clearance, there is an option other than asking for vectors.  Look at the approach and pick out a waypoint or two that will roughly sequence you for arrival as if you were flying the published procedure, and that will put you in a good position to see the runway.  (say a 5-10 mile straight in)  Then make a request to fly direct at your current (or some other) altitude for a visual final.  That way you do the navigation, ATC isn't burdened with vectoring you, and you still get the approach type you want.
For example:
You - "N123Y request present position direct CHUNKS at 3000' for visual approach RW 16."
ATC - "Cleared direct CHUNKS at 3000', you can expect the visual, report field in sight."
You - (when there) "Field in sight."
ATC - "Roger, cleared visual approach RW 16."
ATC is generally pretty good about trying to give you what you want as long as you are clear in the way you are asking it.  They know when the weather is beautiful, and why you might not want to bother with a full instrument approach. And understanding what you want, they might even offer a compromise based on MVA in different sectors, i.e. "Unable direct CHUNKS at 3000', can you accept 4000' to PUKE, then 3000' to CHUNKS for the visual?"

@757toga, thanks for the feedback.  No research required, just 30+ years of flying experience!  I made a minor edit to clarify this point, please let me know if you think it needs more emphasis.

It's perfectly fine to request a visual approach before you have visual reference, just make it clear that you are not ready for the approach yet ("Request visual later on" or something).
ATC may still assign you another type of approach if a visual does not fit in the traffic picture.

In the US a visual approach request is not permission for ATC to issue a visual approach clearance—we need the pilot to explicitly call either the airport or a preceding aircraft "in sight" before issuing the clearance.


text:
Are there any Navions on floats?
I have a friend that is considering putting his Navion on floats. A huge challenge. I recall having seen a photo of a Navion on floats, an old black and white photo, but I can no longer find it. If we can find it, it would be very helpful as he might be able to look up the N number and get FAA records on the engineering, etc.
Can anyone help in find information on Navion float conversions?
Any thoughts on a Navion on floats?

I've seen photos of a DC-3 on floats.  Getting the work done by an appropriately qualified shop and getting the FAA inspector to sign off are the main things involved.

I edited you post, please confirm if I got the right A/C type, as I was unfamiliar with it, and would expect others to have the same issue.

As for thoughts... looks difficult to pull off, unless the gear fittings are overdesigned and will tolerate the torque of a float system. Also, the low wing would give me some pause due to the small wingtip clearances; ground (water) loops are not enjoyable.

Yes, I am discussing a Navion. First made by North American (P-51, etc.), then Ryan (Spirit of St. Louis, etc.) and then a couple of others who bought the type certificate.

It can be done in theory, as can most airplanes if you develop the attachment fittings and the airplane has a reasonably slow takeoff and landing speed.  The Beech 18 has long been used on floats in the bush.
Notwithstanding the fact that it was done once upon a time on a Navion, in the absence of a pre-existing STC, and access to the particular floats covered by it, the costs would be staggering unless you put the airplane into the Experimental category and even there it would be only slightly less than staggering.
I don't see any signs of a float kit that was ever developed for the Navion for Edo or Wipline, and I assume it's a certfied category aircraft, so I'm going with starting from scratch, which means staggering, which means "fuggeddaboudit".
As an ex bush pilot, as far as doing well as a float plane, several comments:
As a thing, in general, low wing float planes suck.  The wings get in the way of docks.
The takeoff and landing speed needs to be reasonably low, ideally below 50 kt.  There is a bit of a hydrodynamic "wall" you hit around that speed while aquaplaning and if you can't lift off before that speed you zoom along seemingly forever building that last few knots, not to mention the concrete like character the water starts to take on.
To have good utility, unless you base it at a lake and only fly to other lakes, the floats should be amphibious, but amphibs on a 4 place airplane leave you with a 2 place airplane (even though you've removed the landing gear).  Straight floats have only a minimal effect on useful load (because credit is taken for the lift generated by the floats plus the removal of the ldg gear), but amphibs are brutal because the weight of landing gear and pumps is ballast.  In the bush you don't see that many working airplanes with amphibs for that reason unless they really need it.
Hull insurance on a straight floatplane is somewhat higher than wheels, but on an amphib, the premium will melt your eyeballs.  Because, maybe sooner or maybe later, just about every single amphib out there will get landed wheels down on water, eventually.
The floats are destabilizing in yaw, and the Navion has a rather smallish rudder/fin, so it will almost certainly need a ventral fin.  Expect to add it to the STC development work.  Only a few sea planes have gotten away with not adding extra fin area.
So, bottom line is, unless you can find an installation STC, and can locate a set of floats covered by the STC, making it just bolt it all together, rig, make a log entry, and fly, it's a gargantuan task that will quickly bring your friend down to earth unless money is no object.

"The floats are destabilizing in yaw" pitch as well, unless I'm missing something? Never mind the larger control authority to contract that effect in pitch.

The floats create a nose-down pitching moment, but the lift force generated by the floats moves the pitching neutral point forward and offsets that to a sufficient extent that no additional band-aids are required on seaplanes.  When you fly a seaplane the existence of the floats below only becomes obvious when doing things like stalls where the pendulous effects can be felt.  The yaw mode is the big one. I used to train ppl in a little floatplane called a Fleet Canuck, which didn't have any xtra fin on floats. It was like a glider in yaw, slithering everywhere if you weren't fast on your feet.

John:  Thank you for your answer. I agree with the entire thing, if that means anything.

"...will get landed wheels down on water, eventually" - I was thinking wheels up on land would be the greater evil. :-\

No, wheels down on water is over on your back every time.  Wheels up on land is grind off a bit of the skeg if on pavement, and no damage at all if on grass.  You can't have a normal gear warning system with amphibs because how is it to know whether the gear should be up or down for a given landing.  Thats one reason the hull insurance premium on an amphib is up there in piston helicopter territory.


text:
How did the Blackops 'quiet one' helicopter muffler work?
Back in the Vietnam War era, special ops needed a quiet means of inserting soldiers behind enemy lines to install eavesdropping equipment. They modified a Hughes 500 to do the job. One of the things done was the addition of a muffler to the jet exhaust. How did it work? It looks very different from the lobes and serrations used to quiet the cores and fan exhaust in turbofan engines.

"I'd stand on the [landing pad] and try to figure out the first time I could hear it and which direction it was coming from. I couldn't place it until it was one or two hundred yards away."

With all recent the interest in municipal vertical flight this might be useful in modern helicopters as they are much more intrusive than this.

Interesting.  Never heard of such a thing!

Basically a large automotive-type muffler. They don't need thrust from it and probably don't mind a small drop in efficiency due to the priorities of the mission. A commercial aircraft is more concerned with performance and fuel efficiency.

@MaxPower Do you have knowledge of its construction or is this opinion?


text:
How to realistically model propeller static thrust?
I am graphing static thrust vs prop diameter for a 600 kW motor and a prop diameter up to 5 m. I have seen the post 'What is the equation for calculating static thrust?' and using its formula and fixed prop efficiency I get a pretty linear graph. At 5 m the thrust is 19 kN.
Structural factors become increasingly important at larger diameters, but what other aerodynamic factors (perhaps prop efficiency changes with diameter) need to be considered to make the graph more realistic?
Update - I assume the prop pitch can adjust to maximize static thrust, but the twist is optimized for high speed (200mph) flight. The engines full power is also available at the best speed for the size of prop being tested. This Equation to bind velocity, thrust and power simplified by assuming unitary engine efficiency is the same as what I have been using.
$$T_0 = \sqrt[\LARGE{3\:}]{P^2\cdot\eta_{Prop}^2\cdot\pi\cdot \frac{d_P^2}{2}\cdot\rho}$$

A paper to estimate static thrust with a C-172 example is here.
Also, a NASA report 447 on calculating static thrust may be of interest.
An Excel spreadsheet to calculate static thrust is here.
There is a SE discussion here and here.
The formula for thrust is...

Where:
F     = thrust (Newton)
d     = prop dia (inch)
rpm   = rotation (per minute)
pitch = pitch (inch)
Vo    = aircraft speed (m/s)

If you want thrust in other units: to convert newtons to grams, multiply newtons by 1000/9.81.  To then convert grams to ounces, multiply grams by 0.035274.  To convert ounces to pounds, divide ounces by 16.
Note: the equation is hard-coded for a "standard day" density at sea level  of 1.225kg/m^3.
The thrust of a propeller is not constant for different flight speeds. Reducing the inflow velocity generally increases the thrust. A reduction of the aircraft speed down to zero tends to increase the thrust even further, but often a rapid loss of thrust can be observed in this regime.
That is why the static thrust of a propeller is not such a terribly important number for a propeller - the picture of a propeller, working under static conditions can be distorted and blurred.
As long as an aircraft does not move, its propeller operates under static conditions. There is no air moving towards the propeller due to the flight speed, the propeller creates its own inflow instead. A propeller, with its chord and twist distribution designed for the operating point under flight conditions, does not perform very well under static conditions. As opposed to a larger helicopter rotor, the flow around the relatively small propeller is heavily distorted and even may be partially separated. From the momentum theory of propellers we learn, that the efficiency at lower speeds is strongly dependent on the power loading (power per disk area), and this ratio for a propeller is much higher than that for a helicopter rotor. We are able to achieve about 80-90% of the thrust, as predicted by momentum theory for the design point, but we can reach only 50% or less of the predicted ideal thrust under static conditions.
Static thrust depends also on the inflow, influenced by the environment of the propeller (fuselage, crosswind, ground clearance). Measurements of static thrust can be easily done, but the theoretical treatment is very complicated and only possible with a lower degree of confidence than calculations in the vicinity of the design point. Due to local flow separation, the behavior of propellers under static conditions can be very sensitive with respect to blade angle settings and airfoil shape.
To get a picture of the bandwidth of static thrust, several older NACA reports and some publications from model magazines have been examined. The results are combined in the following graph.

Source
The Source provided a model airplane example calculation that is applicable to full size aircraft.
We have got two different propellers with a blade angle of 10° and 25° respectively. The first one has a diameter of D = 200 mm, the size of the second one is D = 300 mm. Which one would be better suited to build a VTOL aircraft model? How much thrust can we expect using an .60 engine of 2000 W (assuming a suitable gearbox)?
From the diagram above we read a static thrust parameter of 0.32 [kg^(1/3)/m], respectively 0.1 [kg^(1/3)/m] around the center of the blue band. To calculate the thrust we have to multiply these values with the power P [W] and the diameter D [m] to the power of 2/3. Performing the calculation for the first propeller (10° blade angle) yields T = 0.32*54.288 [N] and thus a static thrust of 17.4 N, whereas the second, larger propeller delivers 0.1*71.138 = 7.1 N only. Using the same engine in a helicopter with its large rotor of 1 m diameter and low pitch angles, would give us a lifting force of more than 55 N !
This example shows, that the diameter of a propeller is as important for static thrust, as it is under flight conditions. But, for static thrust the blade angle is also very important - probably even more important than for the design point, where a gearbox can match almost any propeller pitch and flight speed quite well.

Your first thrust equation uses rpm instead of power which makes it hard to apply to this problem. I have updated the question to include an adjustable pitch prop so outright stalling is not a factor. The "Source" article caption for your diagram states that it shows thrust parameters for props with 2-8 blades, but I could find no legend that tells which datapoints belong to which prop. Are you familiar enough with the material to know?

This basically depends on the prop loading and RPM. If you are not satisfied with the momentum disk theory based results then the next step would be to use blade element theory based calculation.
If I were you I would certainly run few test cases with a known propeller geometry by scaling the propeller. One of the easiest way I can think of doing this is to use QPROP from Prof. Mark Drela at MIT. This is a free software and on top of this it is a command line program which is very well suited for this kind of an activity because all the parameters could be changed on the go, preferably via a bash or python script.
HTH

Am experimenting with Qprop and will respond when I have learned something.


text:
As a commercial pilot, can I fly my spouse for her work?
So I hold a commercial license and have a 2nd class medical.  My wife is an engineer and a product she works on needs to be altitude tested (unrelated to aviation). She was suggesting that we could rent the plane from the flying club I am a member of and she could submit the receipt and get reimbursed for the flight cost. If she wasn't my spouse and was a friend asking me to rent a plane and give her the bill I'm pretty sure this is pretty clearly not OK.
We talked about doing a "pro-rata share" but wasn't sure how that's defined cause... it's my wife - shared finances and all that.  Any experts have any feedback on whether or not we're okay to do this?  Or if we really want to do it do we just eat the cost of the flight ourselves?
EDIT: Clarifying based on comments - This is USA (CPL) and my wife and/or company wouldn't be on the bill. It would be my name because it's a flying club and they would only rent the plane to me.  So it would get charged to a credit card in my name (joint account with my wife) and she'd turn around and get it reimbursed.  I agree, I'm not "holding out" in my opinion... but just trying to make sure I keep things above board.

@dupsatou, I'm not sure why you are concerned about this.  Specifically your comment "If she wasn't my spouse and was a friend asking me to rent a plane and give her the bill I'm pretty sure this is pretty clearly NOT ok."  (emphasis mine)  Why would you think this is not OK?  You earned a commercial pilot's license, you are now entitled to compensation for flying!

Because I'm providing the plane.  I think that's where the main concern is.  If I provide the plane and the service and all doesn't that start to make me an operator?  It's one thing to be hired to fill a role as a pilot in somebody else's aviation department or in somebody's personal plane - it's another for somebody to essentially charter a flight.  I feel like this falls close to chartering a flight - even though it isn't necessary with a destination in mind (we're just going up to 10-12k ft for equipment testing).  You are so in-grained to be careful with your CPL - I just want to be sure

Oh and to add... that's why I think its not okay if it's my wife.  I feel like because my spouse and by extension, her employer, are the one asking it makes it a little bit more gray.

If you are holding out as a common carrier you would definitely need an operating certificate.  However, I am quite confident that an occasional private carriage of the sort you describe is perfectly legal.  And even if it is a slightly gray area, I would consider the probability of it ever even becoming an issue in my decision.

The prohibition you're worried about as a CPL is "holding out" flight services to the general public, which can be summarized as providing both plane and pilot as a package to strangers.
In this case, you would be providing both plane and pilot, so your concern is understandable.  However, there is a clear personal link from you to your wife and via your wife to her employer, i.e. they're not the "general public", so you're okay.  It would even be okay if your customer were a bona fide friend, rather than your wife or her employer.
If the company could rent (or otherwise provide) the plane and separately pay you to fly it, you wouldn't need that personal link.  Given you're renting from a flying club, that's not possible, but it's something to keep in mind for future scenarios.  Do check with the flying club to make sure it's okay with them and their insurer.  I assume you have the appropriate insurance for yourself.
The pro-rata stuff only applies to a PPL, and given the FAA's policy that flight time and even employer goodwill can count as "compensation" even if no money changes hands, a PPL could still get busted even if they "eat the costs" as you propose.  As a CPL, though, you don't have to worry about that, just the "holding out" rule.

After looking into it some more I think you are correct, this was a good answer!  Thank you!


text:
Do 'threshold' and 'end of the runway' mean the same thing?
While I studied aviation, I got confused by these two words.
Can anybody explain whether they're the same or not, and if not, what is the difference?

For the simple case, yes.   The threshold will be the end of the runway.  The AIM has a graphic showing standard markings past the a normal threshold.

However, the airport operator may decide that aircraft should not land at the end of the runway.  This may be temporary (perhaps for construction), or permanently (for obstacle clearance or noise abatement).  In such cases the threshold is moved and marked away from the end of the runway.  When permanent, this is called a displaced threshold and will reduce the landing distance available (LDA) to less than the length of the paved runway.

A.k.a displaced threshold. There are also overrun areas with yellow arrows pointing towards the runway threshold

I look at displaced thresholds the other way: the threshold is put where it needs to be for obstacle clearance, but if the land in front of it is also usable, why not make it available for takeoffs, which require more runway than landings do?

@StephenS In the case depicted in the lower image it is indeed allowed to take off using the section marked with white arrows. However, sometimes it is not allowed (for example if the runway can't handle the weight of aircraft). In this case the term used is "Overrun area" and the marking is yellow chevrons: https://en.wikipedia.org/wiki/Runway#Sections_of_a_runway


text:
Is it legal to rent out an experimental aircraft?
Is it legal to rent out an E-AB aircraft (not a light sport aircraft)?
The aircraft will not be used for hire or compensation but to rent out to a pilot who wants to fly from point A to point B.
After reading the FAR 91.319 I know the answer but seems like a lot of folks in this industry are confused on this topic.

What is the question? If it is legal to rent it?

Yes, is it legal to rent EAB aircraft for personal use.

If you know the answer, please post it.  Stack Exchange welcomes question askers to answer their own questions.

Look, someone already is answering me WRONG, and stating No and using 21.191(I) as the answer.

Since you specifically state the question as it relates to E-AB, the reference to 91.319(f) doesn't apply. But 91.319(a) does apply.
From 91.319, the answer is "no".

§91.319   Aircraft having experimental certificates: Operating
  limitations.
(a) No person may operate an aircraft that has an experimental
  certificate—
(1) For other than the purpose for which the certificate was issued;
  or
(2) Carrying persons or property for compensation or hire.

Your statement that "The aircraft will not be used for hire or compensation but to rent out to a pilot who wants to fly from point A to point B." is where you have erred. The FAA has interpreted that rental (or lease) of an aircraft with or without crew is a commercial operation that is "Carrying persons or property for compensation or hire."
So in the view of the FAA, renting the aircraft is a violation of §91.319 (a)(2).
You should also be aware that you could be violating access rules for your airport by operating a business that doesn't comply with the airport's minimum standards for business. That could get you kicked off the airport.
You also need to consider the conditions of any insurance policy that covers the aircraft.
That said, there's nothing that prohibits you (except possibly insurance) from loaning the aircraft to someone as long as you don't receive any compensation. Just be aware that the FAA interprets the term "Compensation" very broadly; e.g. excess fuel on return of the a/c could be considered compensation.
Final caveat: I'm not an aviation lawyer, so nothing I say should be considered legal advice. Contact the FAA, EAA (since this about E-AB) or an aviation lawyer if you want a more definitive answer.

The only NO I see is under “light sport”

21.191 (I) is light sport I originally asked for anything other than light sport. I specially stated EAB other than light sport, like 21.191(H).

Sounds like a whole bunch of experimental survey aircraft cannot be operated for hire.

Where can I find the FAA interpretation stating renting is operation for hire?  I have seen interpretations that would indicate the opposite.

What is "the purpose for which the certificate is issued"?  I e. Does the certificate specify only for personal use of the owner? (or similar)

There does not appear to be any prohibition against it. 91.319(f) applies to E-LSA but not to E-AB aircraft. 91.319(a)(2) says that no person may operate an experimental aircraft "carrying persons or property for compensation or hire," but numerous FAA interpretations such as the Greenwood interpretation, specifically scenario 6, makes it clear that renting an aircraft is not "carrying persons or property for compensation or hire" as long as you only provide the aircraft and not the flight crew.
The interpretation refers to the 100 hour maintenance not being required, but that rule, 91.409(b), uses the same no carrying people for hire langauge. Renting an aircraft and flying it is not carry passengers or property for compensation or hire, or else renting as a private pilot would be illegal per 61.113!
AOPA has a document on this general topic, which also agrees that E-AB can be made available for leasing under current law. Obviously AOPA documents are not regulatory, but it's at least confirmation that you aren't crazy for reading the regulations the way they're plainly written!
Practically, it's likely you will have problems with insurance for such an operation.


text:
What are the FAA regulations on operating UAVs in class E airspace above FL600?
What are the regulations on flying UAVs (commercial or experimental) above FL600, i.e. in class E airspace above class A? I want to make a HAPS (High Altitude Pseudo Satellite) and operate it in the higher altitudes.
Is there a way to do this without a pilot's license (I don't know if I can pass TSA background checks)? How high do I have to fly to be above class A and in the class E airspace? Would you recommend launching from international waters? And how high should I fly to be in space or in completely unregulated and uncontrolled airspace?

Welcome to Aviation.SE we generally prefer that you keep your posts to a single question (there are a few in the body here). You may want to split them into different questions to avoid this being closed. You can find a tour of our site here

For your final question about where space begins, see this question on space.SE

The FAA limits drone operations to 400 Ft. so getting to FL600 is not really possible.

Cannot be flown higher than 400 feet above ground level (AGL), unless
  flown within a 400-foot radius of a structure and does not fly higher
  than 400 feet above the structure’s immediate uppermost limit;

The FAA does offer a waiver process for flying drones beyond the regular part 107 rules. You can find all the info on that here. The request to operate in controlled airspace form does ask for a max altitude so its possible it can be requested.

However someone in Russia appears to have flown their drone up to FL330 so it may be allowed there.

Can unmanned aircraft be flown higher than 400 ft when accompanied by a chase plane? Not that there are many options for a chase at FL 600, but 400 ft is very restrictive.

@PeterKämpf It seems you can fly them 400 feet off a structure but I dont know of anything that reaches up to 400ft from FL600. I would think you can fly them off a chase plane with approval from the FAA as they can generally offer special approval for most things if you ask.

@PeterKämpf according to this it looks like Government UAS's can apply for a waiver to fly with a chase plane that must remain in visual contact with the UAS.

If control is from the chase aircraft, a waiver would be required in the US.

I guess I should be specific I want to operate it autonomously with ADS-B avoidance and above 72,000 ft. Thanks for the tip on Russia and I also want to have the craft airborne for 3-6 months at a time at least and outfit it with SDR, RF transceiver and high powered telescope. I don't know if this can be accommodated here so I may he looking for other countries to operate in or experiment over international waters above 400ft agl. I'm more looking for a way to sell survaillence via an API, and become an ISP for sea vessels. Would be nice to service land as well but maybe hard legally.

@user9742946, as far as I can think of no aircraft technology is currently in existence will keep a high powered telescope aloft at 72,000ft. for 3-6 months. The closest thing to those parameters is the SR-71 which had 2 high powered cameras on it and needed constant refueling to stay aloft and was quite pricy per flight hour....

You can fly a drone higher than 400 feet under Part 101

To fly your own Unmanned Vehicle in national airspace without a chase plane you need a Certificate of Authorization for that UAV.  See this article here about the Global Hawk which flies above 60,000 feet.  I have no idea how you would go about getting that authorization but I am sure that it won't be trivial.  Global Hawk was tested in restricted military airspace before approval was granted to fly in national airspace.  And yes you would need a remote pilot certificate to operate the UAV see details from the AOPA here.  So you need two things to fly in national airspace:  To certify the aircraft and to get a remote pilot certificate to pilot it.
Testing in International waters would be feasible since international waters is unregulated airspace but you still need to be careful to avoid any international traffic.  The best thing to do is contact the FAA and see what they say about it.  The FAA can be very flexible on accommodating experimental aircraft so it never hurts to ask.


text:
What are the equations to compute takeoff and landing distance?
I am flying a Piper 28-336 Dakota. Based on this paper I was able to reproduce the take-off distances from the POH and incorporate the calculations directly in Excel. It can be seen that the effects of temperature and weight on the takeoff distances are not linear and can be approximated by (with no wind correction and based on the above paper)
$ReferenceDistance\times[(1-Altitude)/145442]^{5.2}\times(273.15+15)/(273.15+Temperature)]^{DensityRatio}$$\times(Weight/3000)^{WeightRatio}$

However for the landing distances it seems that the above formula does not work as the landing distance seems to be more "linear" than the takeoff distances.

Can anyone provide the precise equations to be used for computing the landing distances as a factor of altitude, weight, temperature and winds? Or references that include those equations?

What makes you think that they were created via "precise equations"? Most of those charts are extrapolated from real-world tests. Curve fitting is probably the most "precise" you are going to get.

@RonBeyer it was an assumption made from my side given the explanations I found in the paper I mentioned.

@Ron Beyer: Indeed, I doubt that they even could be determined from "precise equations".  For instance, what is the EXACT coefficient of friction of the runway surface, the EXACT tire pressure and degree of wear,  the EXACT amount of braking force an individual pilot applies...

@jamesqf All models are wrong, but some are useful.

I did this, using Fortran 90 for the math and Tcl/Tk for the plotting.
There is no single equation; instead there are several cycles of calculation nested inside each other like a Russian matryoshka.
The innermost loop calculates all forces and moments at the point in time at which the calculation stands.
The next layer iteratively trims the airplane so control deflections fit the desired rotation rates.
The outer layer integrates the parameters, moves one timestep ahead and applies new boundary conditions.
For the initial climb there is another iteration to adjust acceleration and climb angle such that the airplane is at 1.3 v$_\text{min}$ when it climbs through 50 ft.
Initially, the airplane is on the ground and drag is smaller than thrust, so a forward acceleration remains. When the preselected rotation speed is reached, the elevator is trimmed for an also predetermined rotation rate and time steps are shortened to minimize the error in finding the liftoff time. The whole process is divided in three parts: Ground roll, rotation and initial climb.
For airplanes with a constant speed propeller I even added another loop inside the force calculation to find the proper propeller beta for the current engine torque and airspeed, but that made the code very slow (it ran initially on a Mac SE/30). For most cases I pre-calculated lookup tables and interpolated a lot.
We used this software to determine the tables in the flight manual of a jet trainer and checked correctness with a few points from flight test. It is easy to set a wind speed in software, it is much harder to precisely find out what the average wind speed was when the test ran. Since my software included all effects like trim drag, gear rolling resistance over speed and ground effect, the results were easily confirmed.
Calculating landing distances wasn't much different, only that the calculation started at 1.3 v$_\text{min}$ and 50 ft.
If you want good results, no single force is constant over speed. If you don't mind such niceties, you can average rsp. linearize the forces and use the integrals in this text.
For a very rough estimation, average thrust and drag and calculate how long the engine needs to add energy to the system until kinetic and potential energy have changed from standstill to 1.3 v$_\text{min}$ and 50 ft and back again. This should be sufficient already to find the effect of wind and air temperature on takeoff and landing performance.


text:
What scientific evidence is there about the effectiveness of pre-flight walk-arounds?
As a student pilot, often on my walk-around, I get the impression that there are any number of hazards that could pass me by, simply because I can look at every part on the checklist but I wouldn't necessarily recognise a problem with that part. This idea seems more plausible when I speak to more experienced pilots of the same type, and each of them warns me about checking one thing in particular that's not on the checklist, because they once saw an accident that was caused by a failure there - and crucially, each of them warns me of a different thing.
At the same time, when I read the monthly accident report bulletins, there are several every month where the cause was some part failing in flight, and they either imply that the failure should have been caught in a pre-flight inspection, or they explain why it might not have been visible. In one local incident a few months ago, a pilot made a hard landing and thought he made an extra-careful inspection afterwards, but made a subsequent flight without noticing that both blades of the prop had been shortened and the firewall was crumpled. More generally, taking off with your pitot cover still in place is the stereotypical example of a bad inspection.
Pre-flight inspections seem very error-prone, on the face of it. What evidence is there about how error-prone they are, and what fraction of defects they detect? I'm asking for either scientific experiments under controlled conditions, or statistical analyses of aircraft grounded after unsatisfactory inspections vs. failures in flight. Turning the question around, you might instead answer about how much less safe we would be in GA or air transport if we didn't have pre-flight inspections at all. This related question is pretty relevant, but focuses on checklist items which are forgotten completely: I'm hoping for a more general answer which also includes defects that are not detected even if the checklist is performed correctly.

They aren't meant to detect things like structural failure, but you should be able to notice missing bolts/nuts/safety wires, loose/missing fuel caps, flat tires, pitot tube covers, clogged/blocked static ports, blade damage, structural damage, incorrect fuel, worn brakes/tires, missing/broken antennas, etc. that would keep you from conducting a safe flight.

Related, it might partially address some of your points (like how error-prone they are)

I doubt that you'll find scientific experiments under controlled conditions.  It's  rather like asking is there any proof that looking both ways before crossing the road actually reduces accidents.

Doing a walkaround is more effective than not doing one.   Do you need a scientific study to tell you that?

OK a scientific study where some planes are checked and some deliberately unchecked is not viable, BUT the question also asks about statistics and these may exist.

@Andy Well, yes,  But read the question title.

Every time a pre-flight detects something the matter with a plane, that's evidence of the effectiveness of pre-flights. But that won't result in an incident being reported.

@abelenky It would be nice to have something more to go on than a flat assertion.

@Dan- I have had the same nagging doubts as a student pilot- as Ron points out, there are the obvious things to look for- but it was/is the grey areas that bother- how much movement in the flap rollers is acceptable - it seems like a lot to me- when should I flag it? How much difference in feel is acceptable?  For a while during my training I became very reluctant to fly - was suffering from ground suck I guess. The more I learned about the mechanics of flight, the engine, the instruments and all the things that could go wrong the more anxious i became.

@Dan - continued: I changed from being a student that relished the opportunity learning crosswind technique to a fair-weather pilot. Confidence slowly returned. A key moment was when our mechanic spotted a crack in the nose gear gear. It was a hairline crack that even when it was pointed out to me I had trouble distinguishing from an oil streak. The 55 year old mechanic had eyes (experience) better than me. If he had not seem it there could have been a nasty accident. But the fact that he had this kind of attention to detail was a great reassurance.

You can never prove a cause and effect relationship when the effect does not occur.

"They aren't meant to detect things like structural failure"-- really?  Don't you grab a wingtip and shake it hard, to see if the spar seems broken?  I usually do.

On a rental plane, the main purpose of doing a preflight is to make sure someone else's mistakes aren't blamed on you.  I preflighted a tailwheel plane once and noticed a scuffed wingtip and scuffed wheel rims-- obviously the plane had recently been groundlooped.  The FBO contacted the previous renter, who admantly denied it.  Never heard how it was all resolved.

First off you are required by the FAR's to preform a preflight check,

Sec. 91.7
Civil aircraft airworthiness.
(a) No person may operate a civil aircraft unless it is in an airworthy condition.
(b) The pilot in command of a civil aircraft is responsible for
  determining whether that aircraft is in condition for safe flight. The
  pilot in command shall discontinue the flight when unairworthy
  mechanical, electrical, or structural conditions occur.

Don't forget the Preflight is also about making sure the aircraft is legally airworthy (VFR or IFR minimum equipment) as well as being physically airworthy.
Here is a brief from the FAA on the matter. It has at least one example of an accident that occurred as a result of a bad preflight. According to this Flying Magazine Article 15 accidents have been the result of a bad preflight in the past 10 years (from the publish date of that article). Here is another example as well. Clearly it has lead to accidents in the past but you may have an issue finding any data on times that it has found things and potentially saved lives (as that is often not reported to anyone but the mechanic).
Nasa conducted a study on checklist usage (preflight included) which is along the lines of what you may be looking for.
Here is another FAA article on preflights and has some more specific stats on what you are looking for.

Consider this: NTSB aviation accident data show that in the last 10
  years, poor preflight inspections caused or contributed to 156 general
  aviation accidents and resulted in 41 fatalities.

You can compare that to the total number of other GA accidents for an approximation of how important it is in causing a crash. of When it comes to the FAA a great deal of analysis is carried out on accident data not necessarily preemptively. One of the other analysis issues here as mentioned in the comments is much of the reasons that planes get grounded does not get reported to any official authority (aside from the mechanic) so the data may not be public or easily accessible.
If we include preflight checklists and walk arounds in the same category. Following the Northwest 255 accident that was the result of misunderstanding/misusing pre-flight checklists the NTSB did do a study on preflight (and all checklist) procedures. You can find the study and results report here which includes some stats.

This idea seems more plausible when I speak to more experienced pilots
  of the same type, and each of them warns me about checking one thing
  in particular that's not on the checklist, because they once saw an
  accident that was caused by a failure there - and crucially, each of
  them warns me of a different thing.

This may be more a case of correlation over causation. If you are involved in aviation long enough (especially the older generation that has flown when laws and planes were much different) you see lots of things. Some of the issues they talk about may have been covered by AD's since they encountered them (if you are flying a common airframe like a 172 or PA-28).
As for not finding stuff this will come with how well you know your plane. As you start to fly the plane more and more (you should be training in one plane or at least only one type of plane). Eventually you will begin to know whats where, the POH can help with that, and you will be able to recognize if something is out of place.
I can speak from personal experience that I have delayed many flights due to things I have found on the preflight. I had a cracked cowling bracket, countless low gear struts that needed air, many fuel calls in the rental planes, a fuel vent issue, and one breaks issue.
Of course you will always have human factors present in manned flight.

While this is a good opinion (and I tend to agree with it), the OP specifically asked for verifiable statistical data on the topic.  I don't see any here so...this doesn't really answer the question.

The Flying Mag article quotes some hard stats on accidents caused by preflight issues I am still looking for harder numbers but there is no study I have yet to find.

Also, citing accidents caused by poor preflight inspections isn't useful (for this question) unless those inspections were identified as poor before the accidents -- and unless we generally know how many poor inspections did not result in accidents. Or, another way to say that is: maybe preflight inspections are by their nature poor, but the only ones that are identified as such are the ones after which something went wrong that might have been caught by a hypothetical, unrealistically good inspection.

I was trying to provide data that was as relevant to the question and has been published. From my searching of FAA reports, documents, NTSB summaries and articles this is the best I was able to come up with so far. I will admit that it is not as direct of an answer as I would like but I feel as though its on topic considering the lack of information that seems to be out there on this topic.

This answer does not answer the question. Rather, I'll try to explain why I believe it is unanswerable (on this site at least).

Let $A$ denote having an accident (of any cause), and $I$ denote having a preflight inspection.
This question is basically asking the comparison of two conditional probabilities: $P(A | I)$ and $P(A | \lnot I)$.
Unfortunately nobody reports an event where $\lnot I$ is true, since you're never supposed to skip a preflight inspection.

Another way of looking at it will be, given a proper preflight inspection is done, there can be 3 outcomes:

A potential safety hazard was discovered. The flight was grounded. (We never know if it would have caused an accident)
No hazard was discovered, but the flight ended with an accident anyway.
The flight proceeded safely.

Note that $P(A | I)$ would be (2), while $P(A | \lnot I)$ would be (1) + (2).
However, (1) is not reported. Aircraft maintenance logs are generally not sent to an aviation authority, unless an investigation has opened on that airframe. This precludes scanning a database for (1).
Another word for (1) is how many accidents have been prevented by a walk around.
Airlines can reasonably have this data. They would know how many mechanic inspections are called because their pilots found something unsatisfactory in their walk-around. However I doubt such data is ever published (except for occasional news report), after all, airline pilots are not supposed to find something during their walk-around. If they do, it shows the airline's maintenance is poor.

Your question presupposes that nobody ever admits a real or perceived maintenance shortcoming because they are more concerned about looking bad than about the safety outcomes. However, I often read accident and airprox reports about such incidents, so I find your assumption unconvincing. Second, there are several data gathering and statistical techniques for finding out the truth even when people don't want to admit to embarrassing truths. These have been used for finding the prevalence of other things, for example illicit use of anti-depressants by pilots.

Nearly every pilot publication, whether a book on the subject or an aircraft flight  manual, will address the tropic.  I can't speak to data driven scientific reporting on the subject, largely because much of what's caught on a preflight will never be reported (and thus omitted as data).  I can speak anecdotally, from personal experience doing preflights, and having been flying for nearly four decades: preflights are critical.  Post flights are also very important.
I've operated five airplanes that turned out to have cracked wings.  In two of those cases, the wings separated in flight, killing all aboard.  In the other cases, the cracks were discovered in time to prevent such events.  I have found cracks, leaks, smoking rivets, fuel problems, maintenace errors, objects left in intakes, gear wells, fuel tanks, and other locations; I have found flight controls rigged backward, and once arrived to pick up an aircraft for a search and rescue mission only to discover the elevators missing.
Likewise on post flight, I've found parts of aircraft missing ranging from small exhaust stacks to 15' long fairings.
At this stage, you may not know what to look for, in that you may not catch everything; you may have more to learn, and you will certainly look for more things as you develop experience in general, and expertise with the aircraft that you fly.  Even if you look for anything that doesn't belong, you're performing a critical task.   Aircraft will talk to you: they seldom fail all at once, and will often manifest problems in various ways.  It could be as simple as a smoking rivet; those streaking black lines that appear around rivets and metal seams, and which are really evidence of fretting corrosion and loose or misfit or damaged components.  Aircraft talk to you; a good preflight is about learning how to listen.
Over the years I've found snakes in landing gear, people attempting to stow away, bird nests, and unreported damage.  A minor fuel leak on a 747 turned out to be a cracked spar.  A flap hesitation on a light twin turned out to be the spar cracked in three places: completely through.
I had a conversation one night in a combat area with a pilot who had just nearly run out of fuel.  He'd taken an airplane at night on a reposition flight to another base, and discovered airborne that he did not have the fuel he anticipated.  He attempted to use auxiliary tanks and found them empty.  He was upset.  He was angry at the pilot who flew it last, who did not ensure that the airplane was refueled.  He was angry with me.  I, in turn, was unimpressed with his preflight, non-existent, and his decision to take an airplane that wasn't yet fueled.  A proper preflight would have prevented his near-disaster, and the risk it put him, the aircraft, and others in.  Preflight preparation goes a long way to helping ensure a safe flight.  I don't know the numbers behind it, but I can tell you from experience that it's a critical function, the importance of which should never be underestimated.

This is great anecdotal information but it doesn’t attempt to answer whether there is any scientific evidence that pre-flight walkarounds are beneficial.

During the acceptance trials for WWII bombers in 1935, the Boeing entry crashed on takeoff as the gust locks for the rudder and elevators had not been removed.  This accident was the catalyst for the preflight checklist.  The preflight checks were done but obviously less than rigorously.
Boeing was allowed to use another plane of the same type, which won the competition and is known as the B-17, the legendary Flying Fortress.  Yes, preflights and preflight checklists matter.
-Skip

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text:
Why do hydraulic jack stalls result in pitch up and right roll?
Quoting from page 162 of the book "Fatal traps for helicopter pilots" by Greg Whyte:

Hydraulic jack stall (servo transparency) in (AS-350) helicopter is an aerodynamic phenomenon can occur when the helicopter is flown outside it is normal flight envelope and subjected to positive maneuvering (g-loading).
It results in uncommanded aft and right cyclic and down-collective motion accompanied by pitch up and right roll of the helicopter.

My question:
What is reason for uncommanded aft and right cyclic collective down pitch up and right roll?

A moderately quick search reveals a few pprune threads and an accident report. From these I understood that:
The hydraulic jack stall occurs when the aerodynamic force on the rotor blades exceeds the force the hydraulic actuator can apply.
The actuators are controlling pitch of rotor blades and are applying force to keep the angle of attack high. When the angle of attack gets too high the blades stall which is associated with change in centre of lift creating a moment trying to rotate the blade to lower angle of attack, strong enough to overpower the actuator.
The right pitch moment is because the retreating blades have higher angle of attack and approach stall earlier.
The forward pitch moment is when the stall happens in higher G manoeuvre where the helicopter is pitching up and thus the blades in front are running at higher angle of attack and approach stall earlier. If the stall happens due to overspeed, the pitch moment will be back instead. In either case it will be opposite to the selected cyclic.
The down collective moment is because the angle of attack decreases on the forward (or backward) and right blades, but does not increase on the other ones, so the total lift is reduced.
The behaviour can be considered a good thing as it prevents aerodynamic stall from fully developing. The effect is also similar to what would happen if the actuators were more powerful and aerodynamic stall did fully develop. It can however be more surprising for the pilot since it may happen before vibrations that normally indicate incipient aerodynamic stall. The condition is self-correcting in that the reduction in pitch causes reduction in G loading and thus reduction of the aerodynamic forces, but the drop in performance can obviously be a problem if it happens too low.

Many consider that jack stall is a result of inadequate design since the jacks are not powerful to counter the forces generated.  This is debatable as jack stall has the effect of countering whatever control input is causing the high loads and therefore in some ways, prevents the pilot from tearing the rotor head off the machine. As the accident reports show, in some situations, a jack stall can drive you into the ground very quickly.

@Simon: Indeed, I've noticed that in the linked threads. And don't agree with it since I don't really see a point in having it push the blades further into stall with the same effect on the aircraft behaviour a short while later.

http://www.alexispar...4-8_65LokUp.mpg - please pass the spare underpants.

@Simon: The link is broken. It looks like comming from the thread I already linked too.

OK, thanks.  I'll try to fix it, but as you say, in your link anyway.

@Simon: The actuators only control blade pitch. That won't tear the rotor head off, just push the blades to stall. Which will cause the same forward and right pitch and loss of lift. Somewhat more violently, even.

I was thinking more about extreme g-loading which could cause excessive coning and overspeed?

@Simon: In helicopter, overspeed causes stall. Either aerodynamic or jack depending on the hydraulic pressure. Since the retreating blade stall is most pronounced, it will result in strong right and slight aft pitch and some loss of lift.

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text:
When is an aircraft cleared to land?
In Is there a minimum separation between a landing aircraft and another crossing its runway? it was explained that once an aircraft has clearance to land, that runway is reserved for the exclusive use of that aircraft.
At busy airports you can usually see a long line of four or more airliners descending a glideslope towards a runway.

Image by nustyR AirTeamImages (found via LondonReconnections)
Looking at FlightRadar24, the time between aircraft appears to be of the order of about 85 seconds according to my stopwatch.

It seems as if, by the time the previous aircraft has turned off the runway, the following aircraft has a very short time to obtain clearance or decide to go around.
At what point is each aircraft given clearance to land by ATC?

Nice picture (if you took it). :)

@Farhan: It's a nice image even though I didn't take it. Attibution added below image.

Usually, the clearance is given when the runway is clear of traffic or, at least in Europe, when two conditions are met:

Reduced Runway Separations is in use and the criteria for issuing the landing clearance are met.
The previous traffic will have left the runway when the following aircraft crosses the threshold. (Non-withheld landing clearance)

321.5 Landing clearance need not be withheld until prescribed separation exists
  if there is reasonable assurance that the appropriate separation will exist
  when the aircraft crosses the runway threshold. However, do not clear an
  aircraft to land before a preceding landing aircraft has crossed the runway
  threshold.

Aircraft can also be made aware to expect a late landing clearance.
Clearing multiple aircraft to land in a sequence on the localizer is not used in countries operating under ICAO rules. This is more of an FAA procedure, as described in the other answers.

In the case of the "being made aware to expect a late landing clearance", would following aircraft's PIC be in a "ready to abort" mental mode until clearance is granted (even more then perhaps normal)?

If you use: expect late landing clearance , you let the pilot know that a landing clearance is to be expected, so he would not be in a mental state to expect a go-around.

Also, in the USA, landing clearance can be given to multiple aircraft at once for the same runway- eg. "JetBlue 1203, number two following an Airbus A320 on a two mile final, wind 260 at 8, runway 22 left, cleared to land." This is called "anticipated separation", which allows aircraft to get their landing clearance with much more space. However, in Europe @SentryRaven is correct.

In addition to @SentryRaven's answer, remember that telescopic compression makes that separation seem much smaller than it actually is.
Those aircraft are minutes apart, not seconds, the correct amount of time for one to clear the runway and still give the next a chance to abort the landing if needed.
In other words, the proximity you perceive from that image is an optical illusion, it's not real.

I still have a hard time buying that the second one is minutes away from the photograph...

@Mehrdad having done such photography extensively (until the airport here almost made it impossible) I know these pictures very well. It's what you see during a normal busy approach cycle, which has the aircraft spaced about 90 seconds apart.

Ah, ok, I guess I can believe 90 seconds, but when you said "minutes" (plural) I assumed at least 3 or 4 minutes, which seemed quite a stretch...

@Mehrdad In Europe, minimum separation on the ILS is 3nm, sometimes reduced to 2.5nm under certain conditions (not taking into account wake separation). The average final approach speed of a commercial airliner is around 140-150 GS. 3/140 = 1.285 * 60 = 77 seconds, so the 90 seconds estimate above is quite correct. Depending on available runways and departure spacing, the separation will be inceased to 4-5nm, to make room for departures.

FAA has the following rulings:

(a) Category I aircraft landing behind Category I or II- 3,000 feet.
(b) Category II aircraft landing behind Category I or II- 4,500 feet.
(c) When either is a category III aircraft- 6,000 feet.

This picture shows the separation of Category I, II and III.

Also known as: Reduced Runway Separation in ICAO-land. :)

This is incorrect. Read closer on Same Runway Separation. There is one for successive departures and one for separating arriving aircraft from other aircraft (Arrival or departure). For arriving aircraft, you need to ensure that preceding arrival has cleared of the runway and preceding departure has cross the departure end of the runway. Except during sunset and sunrise, (a) and (b) you quoted apply. But not (c). You just can't separate Cat III arriving by this

Concur with @fjch. This answer (and image) is correct for an arrival behind a departure, not for an arrival behind an arrival.

In the United States, FAA has some quite complicated rules on landing clearance.
Anticipated Seperation
Contrary to the rest of the world, FAA ATC clears aircraft to land unless there is a reason not to; for example, traffic holding in position.

a. Landing clearance to succeeding aircraft in a
  landing sequence need not be withheld if you observe
  the positions of the aircraft and determine that
  prescribed runway separation will exist when the
  aircraft crosses the landing threshold. Issue traffic
  information to the succeeding aircraft if a preceding
  arrival has not been previously reported and when
  traffic will be departing prior to their arrival.
b. Anticipating separation must not be applied
  when conducting LUAW operations, except as
  authorized in paragraph 3−10−5b2. Issue applicable
  traffic information when using this provision.

For departures,

Takeoff clearance needs not be withheld until
  prescribed separation exists if there is a reasonable
  assurance it will exist when the aircraft starts takeoff
  roll.

This means that ATC needs not to wait for the extra few seconds to issue takeoff clearance when we all know that the aircraft taking off won't be able to line up and start takeoff roll until some 10 seconds later.
Same Runway Seperation
In case of issuing landing clearance, preceding arrival has to be cleared of the runway and preceding departure has to have crossed the departure end of the runway.

a. Separate an arriving aircraft from another aircraft using the same runway by ensuring that the arriving aircraft does not cross the landing threshold until one of the following conditions exists [...]

The other aircraft has landed and is clear of
  the runway. [...]
The other aircraft has departed and crossed
  the runway end. [...]

According to AIM 4−3−20 b., The definition of being clear of the runway is not actually crossing the hold short line.

An aircraft is considered clear of the runway when all parts of the aircraft are past the runway edge and there are no restrictions to its continued movement beyond the runway holding position markings.

Except
Landing clearance can sometimes be given even if both aircraft remains on the runway.
At the time of landing traffic crossing the threshold, the following must be ensured if the preceding traffic is departing

If you can determine distances by reference to suitable landmarks and the other aircraft is airborne, it need not have crossed the runway end if the following
  minimum distance from the landing threshold exists:
(a) Category I aircraft landing behind Category I or II− 3,000 feet.
(b) Category II aircraft landing behind Category I or II− 4,500 feet.
(c) When either is a category III aircraft− 6,000 feet. (See FIG 3-10-5.)
[...]

if the preceding traffic has landed.

Between sunrise and sunset, if you can determine distances by reference to suitable landmarks and the other aircraft has landed, it need not be clear of the runway if the following minimum distance from the landing threshold exists:
(a) When a Category I aircraft is landing behind a Category I or II− 3,000 feet.
(b) When a Category II aircraft is landing
  behind a Category I or II− 4,500 feet.

Note the difference between when preceding aircraft is a departure and when it is an arrival. The reason being that Category III aircraft (airliners) is not guaranteed to be able to stop within 6,000 ft and not hit the traffic ahead which is only at taxi speed.
Note that all of the above apply only to the issuance of landing clearance, takeoff clearance follows another set of rules that is quite similar but not all the same.


text:
Are the lift / drag coefficients considered dimensionless?
Since the lift coefficient, $C_L$, and the drag coefficient, $C_D$, are obtained by rescaling the full lift and drag by
$$\frac12 \rho A v^2$$
does that mean they're dimensionless numbers?
It's slightly confusing, because after rescaling, $C_L$ and $C_D$ depend on the angle of attack, $\alpha$, which somehow makes me think of $C_L$ and $C_D$ as dimensionful quantities.

For what it's worth, angles are typically considered dimensionless, too.

Not considered, but defined! Related: Why do we use dimensionless expressions in flight mechanics and aerodynamics?

@Sanchises, yes, but only when they are in radians ;)

If it helps, the Mach number is also dimensionless. And very obviously not a constant.

Fun fact: work and torque both have the same dimensions (Newton-meters), but are very different things: Work / energy is based on a dot product (force in the direction of motion), the other on a cross product (force at a distance from a pivot point).  Unfortunately, the way we've constructed our mathematical formalism for doing physics, dimensional analysis doesn't help us sort out $N \times m$ from $N \cdot m$.

Yes they are dimensionless numbers, which does not mean that they are constants. $C_L$ $C_D$ are variables. Dimensionless meaning: no physical unit. $$L = C_L \cdot \frac{1}{2} \rho V^2 \cdot A$$ with metric units:

L [N] = [kg*m/sec$^2$]
$\rho$ [kg/m$^3$]
V [m/sec]
A [m$^2$]

Dimension of $\rho V^2 \cdot A$ = $\frac{kg}{m^3} \cdot \frac{m^2}{s^2} \cdot m^2 = kg \cdot m / sec^2 = N$

same explanation holds for CD, and very similar for CM, and Ch (hinge moment coefficient), and other aerodynamic coefficients of forces and moments.


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What is this British bomber?
From previous answers this is probably at RAF Duxford in the mid-1930s.

Source: wikimedia.org
I would say an Armstrong Whitworth Whitley.
Somehow the uncommon nose section looks like a special variant, maybe a radar-equipped submarine hunter?

The pictures show Armstrong Whitworth Whitley K7208, built as a Mk I, but used in 1938 as a prototype to test the aircraft with Rolls Royce Merlin engines. The nose and tail turrets were removed and faired over.


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Why does the US Marine Corps fly the Harrier, a VTOL or operationally STOVL aircraft?
The UK flies the Harrier because they have STOBAR carriers, but why does the United States Marine Corps fly the Harrier?

They also fly F-18's, which are not VTOL (they also fly F-35's) and other non-fighter aircraft.

Forward deployed close air support where long runways aren't available.

At the time this question is asked the UK has not operated Harriers for eight years,  has only one commissioned aircraft carrier, and that uses a STOVL configuration.  When the Royal Navy did operate Harriers they flew from carriers that also used the STOVL configuration.

Perhaps because the USMC doesn't have any aircraft carriers?  Not to mention that carriers aren't much use in places like Afganistan :-)

Because when selecting aircraft the requirements were for close air-support and to be able to operate from amphibious assault ships like the USS Tarawa and the USS Nassua.
These ships have very small decks that aren't geared towards launching larger aircraft like the F-18.


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Why do fighter pilots use night vision goggles rather than normal light inside the cockpit?
I've seen military personnel using night vision goggles (NVGs). With their flight altitude, I don't think the enemy can notice them. I thought it may be due to eye strain, but other units use red lights during long jobs that need looking at a screen. Also, you should consider some fighter pilots have short missions and their eyes won't get tired from light.
I wonder why they don't use normal light. Normal light versus red light versus night vision. I never used night vision, but I don't think it's comfortable to use.

former F-18 pilot here, it's my first post here so be kind :)
NVG's are not for domestic use, they are entirely tactical. Here are some uses;

Night formation (Defensive/Offensive counter air missions), such that formation members can fly lights off or in night mode (which we did all the time). Most fighters have external NVG lighting that can't be seen with the naked eye.
Target acquisition (Offensive Strike/CAS etc) in low/no light environments (permits visual rules of engagement upgrades etc
Laser ID. Laser range finders and target acquisition pod lasers can be seen through NVG's, we can conduct visual 'hand-over' procedures using lasers to talk on a wingman to a target. Lasers are weapons and have their own master arm switch, just like the gun, bombs and missiles.

With NVG's, I can see formation members with low/no light dozens of miles away, which can't even be done during the day. This brings enormous tactical advantage in air-air scenarios.
NVG's are not used to see inside the cockpit.
Hope that answers your question!

Welcome to Av.SE! Thanks for posting your first-hand experience -- always great to have here.  Please check back often & share your knowledge on other threads as well.

Are there any certain fighter jets that pilots who fly them becomes cocky or are there certain fighter jets pilots seek to fly. I've heard naval aviators are a bit cocky, cocky in good way of course. I've checked your profile it says Australia, do you guys also have nicknames or that's just US thing. Are there any cultural differences between AUS AF vs USAF

Yes AUS pilots certainly have callsigns. There's also cultural differences. I wouldn't say one is better than the other. AUS works closely with US (our closest military ally for sure) in multiple exercises each year (we have a lot of great airspace for large exercises) so we know each others methods/tactics, and culture well :)

Fighter jets do have a normal cockpit lighting in them. Occasionally crews do use night vision goggles, not for viewing instruments, but visual reference outside the jet, and cockpit lighting can be adjusted for NVS systems. But it is not recommended for all applications to use night vision goggles only, so standard cockpit lighting is provided. In addition normal cockpit lighting is so low that it’s virtually impossible to see an illuminated cockpit from a distance.

I would imagine that one cannot "see paradise by the dashboard lights" when flying at night in any aircraft - it would totally ruin your night vision for seeing outside. I'm always amazed when I can see the expression on the face of a driver that I pass on the highway at night.

The major issue for any combat pilot isn't to see what's going on inside the aircraft, but rather what is going on outside. Wikipedia has some more information on the effects of using red light, but the short version is that the red light preserves night vision while at the same time making it possible to read instruments and labels.
For a combat pilot who might need to watch for other aircraft, fly in formation or close to terrain at night preserving the normal night vision is essential. Night-vision-goggles also helps, but these work primarily by amplifying existing visible light. Adding additional light sources inside the cockpit would have the same effect as if you didn't wear them and turned up all the lights; you'd have no problem seeing inside, but wouldn't see anything outside due to the contrast.


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What is this US Navy airplane seen at Westover AFB?

This Navy aircraft was at Westover AFB in either 1987 or 1990. Type unknown.

I think it should be the T-28C

Thanks very much for your help! I will update my website and my scrapbook!

And the helicopter is an AS350 Écureuil.

@PeterKämpf interesting... that means "squirrel" in French. Thanks!

The full name is a North American T 28 Trojan.

This is already explained in the link in the previous answer. Feel free to edit the info into the existing answer, or post a comment (now that you have more rep) rather than posting another answer that doesn't add much.


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Which altitudes are safest for VFR?
As a fairly new pilot who does a fair amount of x-country flying I find myself "feeling" safer going East at 5500 and West at 6500 happily burning extra fuel to get up there. Listening to the on route frequency position reports as I fly, I find the vast majority of GA traffic fly between 3000 and 4500 giving me the feeling that things are pretty crowded and less safe down there. Is there any validity to this?

What country/region are you flying in?

It depends where you're flying.  Around here (western US), there are plenty of places where to get to 6500 ft MSL, you need to be a miner :-)  And for longer flights, it's often more fuel-efficient to climb to higher altitudes, say 10-14K ft.

@jamesqf, while it is more common in the Western US, in the east and central areas, many pilots do not have oxygen and the equipment for it.  I tend to not encourage flights where it would be appropriate because without the equipment, some pilots may push it.  It should be noted that with mild hypoxia there is a loss of night vision at night, and acuity during the day.  HOWEVER, a note to aspiring high flyers, pulse oximeters are real cheap, like $30 for a quality one, and are reasonably reliable for assessing gross oxygenation levels.

This question is subjective and dependent upon the aircraft type, location, terrain, airspace, winds aloft,  weather, etc which you will encounter.  There is no one ‘safe’ band of altitudes for all cases.

I was at an EAA IMC Club meeting (US) where we meet monthly to discuss IFR, scenarios, questions on approach charts, etc.  Found out there is also an EAA VMC club for VFR pilots, so we ran thru a set of slides that were presented recently. There were a bunch of questions on bird strikes. One that was discussed is that most birds fly at ~3500 feet.  Your strategy of flying at 5500, 6500  to get above the birds and a lot of low flying VFR traffic sounds perfect.  In my area (Boston, MA) the summer clouds always seem to be at 4500, 6500, so climbing above them for smooth air can be a challenge.

@mongo: I'm not talking about flying at altitudes at which normally healthy people would require supplimental oxygen, but the sort of altitudes at which we hike & cross-country ski.

@jamesqf: You mentioned 10-14k  In the US, 14 CFR 91.211 requires supplemental O2 availability from 12.5k to 14k for duration of 30 minutes or more.  That would require O2 equipment. Best practices for many pilots would have O2 available above 10k.  Sure, perhaps not the guys who live in Leadville.  But having O2 equipment is an impediment for many "fairly new" pilots.

Excuse me, 12.5 to 14k, requires the use of O2, not just the availability, for more than 30 minutes.

@CrossRoads, if you have a reference on "most birds fly at ~3500 feet," I would appreciate it.  That is very contrary to the research I was familiar with, which is about 30 years old.

3500 is what was presented from the EAA.  Another was a bird strike at 31,700 feet! Amazing.

The altitude you fly at should be determined by the following:

Where you are safest.  Crossing 5500 foot mountains at 6500 simply is not a good safe practice.  Your altitude should be higher at night, if for nothing else, to give you more time to diagnose a problem or pick a suitable landing spot.  When my primary students fly the hills around here, I insist that their final cruise be above 3000 AGL.  That keeps them out of 2000 foot towers (most are just 1500 feet), and gives them time to pick a landing spot, and gives them altitude for getting radio assistance from FSS or ATC.  Higher is better, but I tend to not encourage 10,000 foot level flights for student pilots because there are other risks.  You should consider all the risks associated with altitude.  Lumbering along at 11,000 feet may not be the least risk option.
Your altitude selection should help you in navigating.  Being up higher lets you pick landmarks, see more VORs, reach more ATC and FSS facilities.  Generally, my students do not use GPS (as student pilots), so if they get lost, they have to descend and read water towers and things like that to find themselves.  That doesn't happen often.
Your altitude should keep you in good weather.  If you are a VFR pilot, you will probably not want to make your trip on top, with a 1000 foot ceiling below you. Again one needs to balance risk.  Being at an altitude which keeps you below the scattered layer, keeps visibility good, and can make a trip more enjoyable.  But if Nervous Nancy is taking her first plane trip, and is predisposed to motion sickness or is simply nervous about bumps, then you want to pick an altitude that will be a bit smoother.

The whole exercise of picking the right altitude, the right route and even the right day is part of a big optimization problem, where you are looking at safety, enjoyment, economics and other factors.  There is no magic altitude, no perfect route.  What is good 80% of the time may be not so good 20% of the time, which is why ADM (Aeronautical Decision Making) is emphasized in training and recurrent training.  Having good visibility, nice tailwinds, a smooth ride and plenty of altitude over the terrain are always nice.
Oh, one exercise you might try...I tend to do this with flight review students...we do airwork at altitude over the hills or low mountains about 25 to 30 miles from the airport.  I pull power and they dive for the nearest pasture, which has down slopes which exceed the descent profile of the aircraft with power off, the gear and flaps down, and heavy slipping.  Or select a field which has an up slope which is extreme enough so that a landing is impossible.  Then I suggest that they try the home airport.  "But it's 20 miles away."  or maybe 25, and they might have a good tailwind at 5000 feet above the airport.  And they start the glide.  On the way we pick alternates, including flat grass strips, along the way.  Almost 100% of the time, the lightly loaded aircraft makes the airport, and they are amazed that they were able to travel so far without power.  And the take-aways are many, which include that having a couple of thousand feet below you really opens up your options.  And to not pick the first field you see.  With altitude, there may be others as you get to more favorable terrain.
I have managed to fly many decades, many hours and never so much as scratched paint on an airplane.  However, before every flight and during every decision, I ask myself what an objective, after the fact, review board would say.

You have to get the concept that there is a "safe" cruising altitude above some level, because that idea bubbling along in the back of your mind will influence decisions, over such things as weather, which can work against you.
The most dangerous area in the VFR world is within a few miles of airports, because you have airplanes on converging tracks and descending, and the vast majority of VFR midairs happen close to an airport, with airplanes converging to the same landing circuit/pattern.
The chance of running into another plane just cruising along over the countryside, even if you aren't looking out for traffic, is microscopic.
That being said, when flying cross country, you go as high as is practical.  The most air miles per gallon is found at the highest altitude you can maintain cruise power, and this this generally around 8000+/- ft, the level you can get 75% power at wide open throttle if you don't have turbocharging.
"Practical" means that what is optimal depends on winds and trip length (leaving out terrain considerations here).  A 12 minute cruise climb to 8 or 8500 feet for a 30 minute trip may not be worth it if you're going to start down again as soon as you get there.  On an hour long plus trip, it is.  Same with winds.  If there are strong tail winds aloft, you may get maximum net MPG by going as high as possible and cruising at less than 75%.  If there are strong head winds, it might be better to go low to maximize ground speed.  For any particular set of conditions, there will be some sweet spot profile that gets you from A to B on the least fuel if you're an owner, or in the shortest time if you're a wet renter paying by Hobbs.
With computer software, it's easy to work out the ideal profile for a trip based on distance and winds aloft and a lot of the nav apps out there have "VNAV" features that do this for you.

The most air miles per gallon is a misnomer, as higher altitudes will generally have higher winds.  In SE piston aircraft, such as training aircraft, the winds can be 20 to 40% of the cruise speed, which imparts a high economic penalty for the increased "efficiency" of higher altitude flight.  Even a direct crosswind will cost.

"Air miles per gallon" is miles through the air mass, without allowing for wind.  Obviously, factoring in the wind changes the net MPG, which I talked about in my second para.

@JohnK: By my count, it's actually your fifth paragraph.

Yeah you're right!  I had a brain fart and was counting up from the bottom. Weird.

Go where you feel safest, terrain will certainly play a role (and be aware of migratory bird habits too!), as well as clouds and your ability to follow landmarks.  Amazing how tiny even a runway can look from 6000 feet, and hazy/humid conditions can make it much worse.
If you are flying VFR, with other traffic flying in the same direction, they should be easy to see, especially if you have more than one set of eyes out the window. Resource your passenger(s) and monitor local radio for traffic.
Chances are, if things "are pretty crowded" you may be flying into controlled airspace.
Otherwise, that situation is not the time to save your light bulbs.  Especially if flying out of the sun, light them up, and weave a bit if flying into the sun.
Your thoughts on changing altitude to avoid traffic are sound.

It's very possible. You'd also have more gliding range higher up. However, you're always going to be safer above 10,000 on flight following because of the transponder requirement.

In which country? According to which rule?

@VladimirF I think Dan means because you'll have direct help from someone with knowledge of winds and visibility, who is tracking you.  That advice, plus the altitude, greatly increases your chance of gliding to an airport with services.

@Harper I agree, but that is country (or airspace) specific, so that's why I asked. In the meantime I looked up some materials and it appears to be about USA. But it wasn't explicitly indicated.

Yeah sorry, I am a true American....I assume everyone else is too. My mistake.

authors: Vladimir F Героям слава


text:
What is the battery voltage for a Supermarine Spitfire?
I am used to modern aircraft being 28V systems. I found an article saying that a trolley AC plug in battery used to start WWII aircraft was 12V. I'm trying to confirm or disprove this.

That wouldn't be surprising as the cars of the time were 6V.

This aircraft museum says that the "Trolley Acc" (Trolley Accumulator) used for Spitfires and other aircraft supplied 12 volts. Lots of sources state that Spitfires had 12 volt electrical systems, including the Pilot's Manual.


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In an F-18, how do rudders deflect during cross winds and gusts? Can rudders be deflected by different angles?
Deflection of rudders can balance moment about the centre of gravity. I have thought of non-symmetric deflection of rudders so that net sideward force is create to balance the moment about the center of gravity of the aircraft.

Any reason you are combining the one-engine-out and the crosswind?  Could it perhaps be better to ask separately?  Just a thought.  If you want to combine, shouldn't we know if crosswind is on same side or opposite as failed engine?  Are we using the wing-down method of correction or kick-out-the-crab?  Which does a jet fighter typically use anyway, or does it just land crabbed? Or is the landing speed so high that for all practical purposes there is never a crosswind component? Kind of hard to give a good answer to your question unless we know some of these things.

I see grounds for some new ASE questions there, if they aren't duplicates-- you might consider asking them--

@quietflyer i will edit the question.actually i combined two different questions

Anyway welcome to ASE-- oh now I see you were asking about each thing separately not saying both were happening at once.

@quietflyer thank you, and please clarify my doubt in details.

Are you essentially asking the same question as this-- which never has been answered -- https://aviation.stackexchange.com/questions/70579/fighter-jet-with-two-rudders-the-deflection-angle-it-is-not-identical-one-have

@quietflyer my question is somewhat differen,im askiung how f18 tackles cross winds using gust, the reason why i mentioned unsymmetrical deflection of rudders is to know if this is possible then it can be answer to my main question

@quietflyer leave the second part and can you please answer the first one

Are you asking from a pilot standpoint, or a software programming standpoint?  Because I'm pretty sure the pilot cannot deflect them differently, but I could confirm with friends if you have good reason to believe that it might be possible.

Considering that deflecting the rudder creates drag as well as sideforce, to maximize yaw torque per unit of extra drag it seems that there might be an argument for deflecting only the one that moves outward and not the one that moves inward.  I.e. treat the rudders like wingtip drag devices and only move the one that is on side of intended direction of yaw.  Is this essentially what you are asking?  If so feel free to "borrow" any part of this comment into your question.  Of course I can also see an argument for deflecting two surfaces a small amount rather than one a larger amount.

As being angled (V-shape), there is a chance rudder react to pitch input such as in this video. combination of both pitch input and rudder input can create asymmetric deflections.

@ManuH -- right, the rudders are both deflected inward for takeoff.  The V-shaped tilt of the tails would also make this plane a bad candidate for deflecting rudders differentially for the reason I suggested above, in any situation where you DONT want to induce a nose-up pitch torque by the rudder deflection.  And I'm still not sure exactly what the original question is intended to be.

"The V-shaped tilt of the tails would also make this plane a bad candidate for deflecting rudders differentially for the reason I suggested above, in any situation where you DONT want to induce a nose-up pitch torque by the rudder deflection."-- unless of course you mix an an elevator (stabilator) deflection as well...

The Hornet has a fly-by-wire flight control system that is run by 2 flight control computers (also known as Roll Pitch Yaw computers) and these each have 2 channels. This system gets pilot input from the controls but the computers will decide the most efficient way to impart the command signal using all of the available control surfaces. Pilot has no say in which surface moves. If they did, this aircraft would be a nightmare to control because, like most modern fighter jets, it has been designed to be inherently unstable. This allows it to be highly manoeuvrable during a dogfight.
Some of the surfaces are controlled by 2 channels (rudder, aileron, leading edge flaps). Some are quad redundant, utilising all 4 channels (Trailing Edge Flaps, Horizontal Stabs).
All of the surfaces, with the exception of the leading edge flaps from memory (because they are connected mechanically with a rod???), can deflect independently of each other, if the software/flight envelope permits. For example, if you want to roll a Hornet, some combination of all or some of the following surfaces may deflect: L and R Aileron, L and R Trailing Edge Flaps, L and R Horizontal Stabilisers. There are various sensors such as accelerometers which provide the negative feedback loop required to ensure the aircraft is getting to the required attitude at the expected rate. If it isn't, surfaces may deflect more or others may be commanded to help out. The circuitry inside the computer is basically a summing amp with the following inputs: command signal from the pilot, the position feedback from the surface and the rate feedback from the accelerometers. I think the important thing to understand is that this signal is nulled (0 volts) when the aircraft is pointing in the commanded attitude. That means no more movement of the surface.
With regards to rudder on takeoff, these accelerometers would sense an uncommanded change in the yaw axis and I suspect the flight control computers would damp this affect using the feedback method described above without the pilot really noticing much, certainly not having to stomp on a rudder pedal to compensate. There would be some sort of signal processing delay and mechanical reactive delay to correct the movement but this is all done without pilot input.
The rudders don't have to deflect symmetrically as they are controlled by different flight control computer channel pairs, one from each computer for redundancy. In fact, when the rudder fails, it is commanded to streamline and the other surfaces will compensate. The software programming inside the flight control computers that determines which surface/surfaces move and by how much.

“because, like all fighter jets, it has been designed to be inherently unstable”—F-18 was probably the second one that was, after F-16. Before F-16 fighter jets used mechanical controls and were designed to be stable in pitch, otherwise they wouldn't be controllable.

… which means the F-15 accident actually demonstrates nothing, because F-15 did not use fly-by-wire controls. It did use differential elevators for roll control, which was important in that accident, but it was a mechanical link.

I'll edit the f-15 part. I was taught this in avionics school but I was taught wrong because I think my instructor must have assumed it was the E variant.

The Negev collision happened three years before the E variant first flew, so it indeed couldn't have been that.